I am receiving these codes when I am submitting my return. I have all my tax-exempt income entered as I worked on a reserve. It talks about filling out a T90 form but it is filled out. All it consists of is my tax-exempt employment income. My T4 has a box71 which seems like I have to enter it. (Seen discussions where you don't enter it) If I don't enter it I get an error on my t4 to fix.